1. Field of the Invention
This invention relates to safety razors and more particularly to blade units of the type arranged for detachable connection to a cooperating handle component, the blade unit including a blade member and a cooperating guard member.
2. Description of the Prior Art
It is frequently desirable to provide a construction in a safety razor which enables the user to adjust the shaving geometry to suit his individual preferences and/or shaving requirements. Significant components of that shaving geometry include "blade tangent angle", "exposure" and "span".
"Blade tangent angle" is defined as the angle between the bisector of the included angle of a cutting edge and a line from the cutting edge to the point of tangency of the skin engaging surface immediately forward of that cutting edge. For example, in a two bladed tandem acting system, the guard is the "skin engaging surface immediately forward" of the first acting cutting edge and the first cutting edge is the "skin engaging surface immediately forward" of the second cutting edge.
"Exposure" is defined as the distance from a cutting edge to a reference plane of a line connecting the points of tangency of the skin engaging surfaces immediately in front of and behind the cutting edge, the distance being measured perpendicularly to the reference plane or line.
The exposure is considered positive when the cutting edge is located on the outer or skin side of the reference plane and is considered negative when the cutting edge is further from the skin than that plane.
"Span" is defined as the distance between a cutting edge and the point of tangency of the skin engaging surface forward of the cutting edge.
Blade units of the type which include a blade and guard member as a unit adapted for connection to a separate handle member provide the advantages of a compact structure in which appropriate shaving geometry relationships are established and maintained throughout the useful life of the blade unit. It is desirable that the shaving geometry be selectively adjustable to suit particular users, however a number of problems arise in a blade unit construction of this type in which a shaving geometry adjustment is provided. For example, the adjustment must be easy to make and permit a wide range of shaving geometries, while not creating any potentially hazardous condition for the user; the incremental production cost of the adjustable feature, to the extent that it is incorporated in the replaceable blade unit, must be minimal in order to be economically competitive; the blade unit must be compact; and the adjustable feature must not unduly complicate the blade unit structure. A number of proposals for adjustment of blade units of this type have been made, for example, as shown in German Offenlinguneschrift 2251633. The adjustment arrangements there shown employ auxiliary blade unit structure which is engaged by adjustment structure when the blade unit is attached to a handle component. Another example of proposals for adjustment of blade units of this type appears in U.S. application Ser. No. 432,842, filed Jan. 14, 1974 in the name of Chester F. Jacobson. The adjustment arrangements there shown employ pivoting means, permitting the guard or blade to be pivoted relative to the other.